Electrical Performance and Reliability Improvement of Amorphous-Indium-Gallium-Zinc-Oxide Thin-Film Transistors with HfO₂ Gate Dielectrics by CF₄ Plasma Treatment.

Ching-Lin Fan,Chiao-Yuan Tseng,Fan-Ping Tseng

doi:10.3390/ma11050824

Ching-Lin Fan, Chiao-Yuan Tseng + Show 1 more

Open Access

https://doi.org/10.3390/ma11050824

Copy DOI

Journal: Materials	Publication Date: May 17, 2018
Citations: 17	License type: CC BY 4.0

Affiliation: National Taiwan University of Science and Technology

Abstract

In this work, amorphous indium-gallium-zinc oxide thin-film transistors (a-IGZO TFTs) with a HfO2 gate insulator and CF4 plasma treatment was demonstrated for the first time. Through the plasma treatment, both the electrical performance and reliability of the a-IGZO TFT with HfO2 gate dielectric were improved. The carrier mobility significantly increased by 80.8%, from 30.2 cm2/V∙s (without treatment) to 54.6 cm2/V∙s (with CF4 plasma treatment), which is due to the incorporated fluorine not only providing an extra electron to the IGZO, but also passivating the interface trap density. In addition, the reliability of the a-IGZO TFT with HfO2 gate dielectric has also been improved by the CF4 plasma treatment. By applying the CF4 plasma treatment to the a-IGZO TFT, the hysteresis effect of the device has been improved and the device’s immunity against moisture from the ambient atmosphere has been enhanced. It is believed that the CF4 plasma treatment not only significantly improves the electrical performance of a-IGZO TFT with HfO2 gate dielectric, but also enhances the device’s reliability.

Highlights

Amorphous indium-gallium-zinc oxide thin-film transistors (a-IGZO TFT) have attracted considerable attention in flat-panel displays (FPDs), because of its advantages, including high carrier mobility (>10 cm2 /V·s), good uniformity in large-area deposition and low temperature fabrication [1,2,3,4,5]
After the CF4 plasma treatment of the active layer, the carrier mobility significantly improved from 30.2 cm2 /V·s to 54.6 cm2 /V·s
We have demonstrated that the CF plasma treatment can significantly improve the electrical

Summary

Introduction

Amorphous indium-gallium-zinc oxide thin-film transistors (a-IGZO TFT) have attracted considerable attention in flat-panel displays (FPDs), because of its advantages, including high carrier mobility (>10 cm2 /V·s), good uniformity in large-area deposition and low temperature fabrication [1,2,3,4,5]. In order to increase the carrier mobility of the a-IGZO TFT, many previous researchers used a high dielectric constant (high-k) material as the gate insulator to improve the electrical performance of a-IGZO TFT [6,7,8,9,10,11]. Materials 2018, 11, 824 direction, which is opposite to the a-IGZO TFT with a SiO2 gate insulator [18,19] This is due to the electron density generated by the density of states (DOS) near the dielectric/channel layer interface or from absorbed moisture from the air. The improvement is attributed to the extra electrons generated in the IGZO film and the DOS near the gate insulator/channel interface passivated by the incorporation of fluorine. It was found that the CF4 plasma treated a-IGZO TFT has higher immunity against ambient moisture

Device Fabrication

Discussion

15 W 20 s

Hysteresis thin‐film

Conclusions